According to a review article from the National Cancer Institute in the US, and research at the Children's University Hospital, Heidelberg, Germany:

Genistein, a plant-based isoflavone, delivers a one-two punch to cancer cells by reducing their ability to from new blood vessels and by attacking the cells reproduction mechanism. Without a growing blood supply, and unable to make new cells, the cancer slowly shrinks and dies.

Organic Fermented Soy (Miso) Kills Cancer Cells

According to Dr. Mercola, most soy products have been linked to breast cancer and brain damage, however organic fermented soy is an exception.

As Mercola points out, “You may have heard that Japanese people live longer and have lower rates of cancer than Americans because they eat so much soy — but it's primarily fermented soy that they consume, and it's always been that way.”